U3020Control Module Wake-up Circuit B High
- Generic OBD-II code · Network
- How the car detects it
- U3020 sets when wake-up line B stays above its valid level, typically through contact with a battery or ignition feed, or because its source holds it on. The practical effect differs from U301F: a permanently active B line keeps asking the module to stay awake even when line A and the bus have gone quiet, so the module cannot enter sleep and the 12 V battery runs down while parked. Ford's 2019 hybrid OBD summary shows how much a high wake level can trigger, since its battery module starts contactor checks whenever the charge wake-up is high. At the same time a transceiver such as NXP's TJA1043 only wakes on a level change, so the fixed high line cannot pass on a real request from source B. No manufacturer documents U3020 publicly. A parasitic draw test with the line unplugged confirms the cause.
- What you may notice
- 12 V battery flat after parking
- Module stays awake with the vehicle locked
- Likely causes
- LikelyWake-up wire B shorted to a battery or ignition feed
- PossibleSource on line B holding its output on
- RareMoisture bridging line B to a supply pin
- Repair
- Medium · Usually a job for a workshop.Typical cost: €50 – €600
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.